The treatment of diseases of long bones often requires the removal of a portion or all of the diseased bone.
For example, removal of necrotic bone tissue is considered to be an important part of the treatment of osteonecrosis of the femoral head. Osteonecrosis of the femoral head is a disease caused by the occlusion of blood flow to or within the femoral head, which leads to the progressive necrosis of bone in the load bearing region. In osteonecrosis, as the bone dies, a lesion is formed below the subchondral bone. The lesion will grow until there is insufficient structural support of the subchondral bone and the femoral head collapses in the load bearing area. Early detection and intervention, particularly by removal of all of the necrotic bone, has been shown to retard and/or reverse the progression of the disease.
One method of treatment for osteonecrosis of the femoral head is core decompression. Core decompression, for example, can be performed by using a trephine or drill to remove a cylindrical core from within the femoral head. The trephine or drill is introduced into the femoral head through a lateral approach extending from the lateral cortex, typically distal to the greater trochanter, through the neck and into the necrotic region. Such core decompression procedure is performed under fluoroscopy to target necrotic regions. Necrotic bone may signal osteoclasts to initiate bone remodeling, but in osteonecrosis the remodeling mechanism is inhibited so necrotic bone may be removed without concurrent replacement. This will lead to collapse of the femoral head. The core decompression removes portions of the necrotic bone, thereby creating pathways to healthy bone structures and prompting the initiation of remodeling. The procedure only moderately targets the necrotic bone and does not remove all necrotic regions. The remaining necrotic regions may inhibit complete remodeling of the femoral head. The use of a trephine or drill to perform core decompression also has the risk of perforating the cartilage if the trephine or drill is inserted too deeply.
Core decompression also can include the use of a high speed burr and endoscope. For instance, after the cylindrical core is removed with the trephine or drill, a high speed spherical burr is introduced into the femoral head. This procedure is performed under fluoroscopy to avoid perforation, which increases the radiation exposure for the surgeon. Bone beyond the boundary of the cylindrical walls of the osseous tunnel is removed as the burr is moved around. To determine the amount of bone removed, the burr is removed and the endoscope is introduced into the head for visualization of the cavity. The alternation between the burr and endoscope is repeated many times, which significantly slows the procedure. In addition, since the cutting is not performed under real-time, direct visualization, the risk of penetrating the subchondral bone and perforating the articular cartilage as well as the removal of healthy bone is very high. In addition, the reach of the burr of the typical instrument used for bone decompression beyond the walls of the osseous tunnel is limited by the amount the shaft of the burr can be angled within the tunnel, thereby preventing the removal of all necrotic bone.
Further, a more invasive core decompression procedure involves exposing the femoral neck through an open anterior approach, and cutting an access window in the neck through which a series of small curettes and/or powered burr are introduced and the necrotic bone removed. In addition to being particularly invasive, such bone decompression technique is slow, and risks perforating the articular cartilage and removal of healthy bone.
Another therapeutic technique can include removal of a cylindrical core using a trephine or drill, and then implanting a vascular graft obtained from the fibula in the space that the core had occupied. The vascular graft is reattached to the circulatory system and provides structural support for the collapsed head as well as an osteoinductive scaffold to enable bone remodeling. Although this fibular grafting procedure has a relatively high success rate, which is attributable to the increase of blood flow in the femoral head, the duration of the surgical procedure is relatively lengthy, and may last up to four hours.
Therefore, there exists a need for method and apparatus for performing tissue removal, such as from the femoral head, precisely and with minimal invasiveness.